Refrigerant composition containing dichloromonofluoromethane

ABSTRACT

The present invention provides a refrigerant composition including dichloromonofluoromethane and one or more fluoroalkyl compounds selected from trifluoromethane, pentafluoroethane, monochlorodifluoromethane, and 1-chloro-1,1-difluoroethane, this refrigerant composition having a considerably reduced depletion potential of ozone in the ozonosphere, achieving a satisfactory refrigerating temperature, and preventing seizing of the compressor of a refrigerating system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to refrigerant compositions for use inrefrigerating systems, and which have considerably reduced potential forozone-depletion of the ozonosphere.

2. Description of the Prior Art

Conventionally, halogenated hydrocarbon refrigerants have been used asrefrigerants for refrigerating systems. Among them, typically used areR-12 (dichlorodifluoromethane) and R-500 [an azeotropic mixture of R-12and R-152a (1,1-difluoroethane)].

Under atmospheric pressure, the boiling points of R-12 and R-500 are-29.65° C. and -33.45° C., respectively, which are suitable forrefrigerating systems. Further, even if their compressor inlettemperatures are comparatively high, their compressor outlettemperatures do not rise so high as to cause oil-sludge in thecompressor. In addition, R-12 is highly compatible with an compressoroil, and hence plays a role of returning the entrained oil existing in arefrigerant circuit to the compressor.

However, the above refrigerants have high ozone-depletion potentials,and when released in the atmosphere and reached the ozonosphere, theydestroy ozone of the ozonosphere. This destruction is caused by chlorineof refrigerant molecules.

To solve this problem, refrigerants excluding chlorine, for example,R-125 (pentafluoroethane, CHF₂ CF₃ ), R-134a (1,1,1,2-tetrafluoroethane,CH₂ FCF₃), and R-23 (trifluoromethane, CF₃ H) are considered to bealternative refrigerants. Boiling points of R-125, R-134a and R-23 are-48° C., -26° C. and -82.05° C., respectively under atmosphericpressure.

R-22 (monochlorodifluoromethane, CClF₂ H) and R-142b(1-chloro-1,1-difluoroethane, C₂ ClF₂ H₃) contain chlorine moleculestherein. However, they rarely destroy ozone of the ozonosphere becauseof their decomposition before reaching there with the help of hydrogen(H) contained therein. Boiling points of R-22 and R-142b are -40.75° C.and -9.8° C., respectively under atmospheric pressure.

U.S. Pat. No. 4,810,403, for example, discloses some blends of the aboverefrigerants not adversely affecting the ozonosphere, each of which is acombination of two or more of the above refrigerants.

However, such blends of the refrigerants as disclosed in the above U.S.Pat. have the following disadvantages. The blends of R-125 R-134a, orR-23 are extremely poor in compatibility with compressor oils used in arefrigerating cycle because the compatibility with the oils dependsmainly upon chlorine (Cl) of the refrigerants. As well, the blends ofR-22 or R-142b, although they contain chlorine, do not exhibitsatisfactory compatibility with naphthene or paraffin oils.

Where a refrigerant has poor compatibility with a compressor oil,separation into two phases (oil and refrigerant) occurs in an evaporatorso that the oil scarcely returns to the compressor, with the result thatbearing portions of the compressor may seize. In addition, the oilbecomes liable to adhere to the piping of the refrigerating circuit,resulting in blockage of the refrigerating circuit.

The lower the boiling point of a blended refrigerant, the moreconspicuous becomes this tendency. Especially, a serious problem existsin application of the blended refrigerants to a refrigerating systemrequiring a refrigerating temperature of lower than -20° C., forexample, -40° C. or -80° C.

Japanese Published Unexamined Patent Application Hei 1-141982 disclosesa blended composition of R-134a and dichloromonofluoromethane (R-21) andteaches its application to refrigerating systems. However, where such acomposition is used as a refrigerant, a refrigerating temperature of-40° C. or -80° C. cannot be attained.

Where R-22 is singly used as a refrigerant, a compressor inlettemperature thereof is required to be considerably lowered so as torepress rise of a compressor outlet temperature thereof. However,blending R-142b with R-22 makes it possible to lower the outlettemperature because the outlet temperature of R-142b does not rise sohigh even if its inlet temperature is comparatively high.

Further, blending R-142b with R-22 forms a nonflammable compositiondespite the flammability of R-142b thereby improving in safety. FIG. 4shows flammability relative to mixing ratios of R-142b, R-22, and air,wherein the hatched area is a flammable area while the other area beingan nonflammable area. It can be understood from this figure that mixingmore than 10 wt % of R-22 can avoid the flammable area of R-142b.

When an ambient temperature is low, for example, less than 0° C. inwinter, in case that refrigerant leakage from the refrigerant circuitoccurs, and R-22 having a lower boiling point precedently evaporates anddissipates. Therefore, R-142b remains solely or dissolved in thecompressor oil. If the refrigerant temperature subsequently is raiseddue to rise of the ambient temperature, bringing a torch for repairingclose to the refrigerant, or the like, only the flammable R-142b flowsout, resulting in an eventual explosion thereof.

The present invention aims to overcome the various problems ascribed tothe prior art as described above.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a refrigerant compositioncomprising dichloromonofluoromethane (R-21) and at least one fluoroalkylcompound selected from the group consisting of trifluoromethane (R-23),pentafluoroethane (R-125), monochlorodifluoromethane (R-22), and1-chloro-1,1-difluoroethane (R-142b).

This invention is accomplished on the basis of a discovery whereinblending dichloromonofluoromethane (R-21) with the fluoroalkyl compoundsselected from the above compound group can yield refrigerantcompositions with significantly reduced ozone-depletion potentials ofthe ozonosphere, capable of realizing very low refrigeratingtemperatures such as -40° C. or -80° C., and highly compatible withcompressor oils.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are each an explanatory view of a refrigerant circuit usedin an example of the invention.

FIG. 3 is a view showing a nonflammable area of R-142b in a mixture ofR-142b, R-21, and air.

FIG. 4 is a view showing a nonflammable area of R-142b in a mixture ofR-142b, R-22, and air.

FIG. 5 is a graph showing a relationship among component ratio of R-21in a blended refrigerant of R-22, R-142b, and R-21, an compressortemperature, and a refrigerating temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refrigerant compositions according to the invention are classified intoEmbodiments 1 and 2. Embodiment 1 consists of blends ofdichloromonofluoromethane (R-21) with trifluoromethane (R-23) and/orpentafluoroethane (R-125) which are fluoroalkyl compounds with nochlorine in their molecules. Embodiment 2 consists of blends ofdichloromonofluoromethane (R-21) with monochlorodifluoromethane (R-22)and/or 1-chloro-1,1-difluoroethane (R-142b) which are fluoroalkylcompounds containing chlorine and hydrogen in their molecules.

In the above Embodiment 1, R-21 content in the compositions is suitably0.1-50 wt %. Especially in the composition blended R-21 with R-23, R-21content is preferably 30-50 wt %, most preferably 35-45 wt %.

In the above R-21 content range of 30-50 wt %, the refrigerantcompositions which are highly compatible with oils and capable ofrealizing refrigerating temperatures of -80° C. or below can beprepared.

In the above Embodiment 2, R-21 content is suitably 0.1-50 wt % which isidentical to that in Embodiment 1. However, from the point of view oflowering compressor outlet temperatures of the refrigerants so as toprevent the compressor from seizing as completely as possible, contentsof R-21, R-22, and R-142b in the refrigerant compositions are preferably2-12 wt %, 50-93 wt %, and 5-48 wt %, respectively. In the abovepreferable contents, the refrigerant compositions which are highlycompatible with oils and capable of realizing refrigerating temperaturesof -40° C. or below can be prepared. Besides, their compressor outlettemperatures are less than 160° C. Contents of R-21, R-22, and R-142bare more preferably 3-7 wt %, 67-74 wt %, and 23-28 wt %, respectively.

R-21 in the refrigerant compositions of the invention contains chlorine(Cl),which however coexists with hydrogen (H). Therefore, R-21 isdecomposed before reaching the ozonosphere whereby its ozone depletionpotential can considerably reduced. Further, R-21 is very compatiblewith compressor oils of the refrigerating cycle so that blending it withlow compatible refrigerants such as R-125, R-23, R-22, and R-142b causesthe oils entrained in the refrigerant circuit to be dissolved in R21 forreturning the oils to the compressor. Still further, since the boilingpoint of R-21 is +8.95° C. under the atmospheric pressure, it evaporatesin the compressor to cool the compressor.

In addition, blending R-21 with R-142b makes it possible to form anonflammable area of R-142b (non-hatched area) as shown In FIG. 3, whichis the same function as R-22. Therefore, even after the dissipation ofR-22 caused by leakage of the refrigerant as described above, R-21remains together with R-142b in the refrigerant circuit so that theremaining refrigerant composition is kept nonflammable, whereby anexplosion thereof can be prevented.

This explosion-proof effect becomes more effective as the weight ratioof R-21 to R-142b grows larger. However, since the boiling point of R-21is relatively high, too much weight ratio of R-21 degrades therefrigerating capability so that required refrigerating temperaturescannot be obtained. According to our experiments, blending 5-20 wt % ofR-21 relative to R-142b could make explosion-proof refrigerants withoutdegrading the refrigerating capabilities thereof.

As a result of further intensive research, the inventor has discoveredthe most effective proportion of the contents, i.e., 70 wt % of R-22, 25wt % of R-142b, and 5 % of R-21. The refrigerant of this proportion isthe most safe and can realize the required temperature (at least -40°C.) for a refrigerator.

Incidentally, R-134a is compatible with alkylbenzoic oils within anappropriate range, therefore, it effects the oil-returning function assimilarly as R-21 does. Besides according to the experiments, theboiling point of R-134a contained in the refrigerant composition was-30° C. or less in the case that the refrigerant contents were 70 wt %of R-22, 25 wt % of R-142b, and 5 % of R-134a.

EXAMPLE

Hereinafter, examples of the invention will be explained in conjunctionwith drawings. FIG. 1 shows a refrigerant circuit of a commonrefrigerating cycle. A compressor 1 driven by a motor, a condenser 2, acapillary tube 3, and an evaporator 4 are sequentially connected. Thecompressor 1 is adapted to use naphthene, alkylbenzene, or paraffin oilsas hydraulic oils. In this example, used is an alkylbenzene oil (CF-32;IDEMITSU KOSAN CO., LTD.). This refrigerating circuit is charged with ablended refrigerant of 90 % of R-125 and 10 wt % of R-21. Anotherpossible blended refrigerant to be charged in the circuit is a blend of60 wt % of R-23 and 40 wt % of R-21.

Now, to be explained is an operation of the refrigerating circuit shownin FIG. 1. The refrigerant composition of a high temperature and highpressure flowed out of the compressor 1 in a gaseous form flows into thecondenser 2 to dissipate its heat and to be liquefied. The refrigerantcomposition is then reduced its pressure at the capillary tube 3 andflows into the evaporator 4 where it evaporates so that refrigerationcan be performed, followed by returning to the compressor 1. However, asthe boiling point of R-21 is relatively high as described above, itreturns to the compressor 1 in a liquid form with the compressor oildissolved thereinto, and evaporates at last in the compressor 1 therebycooling it. As a result, the oil existing in the refrigerant circuit canreturn to the compressor 1, and at the same time the compressor outlettemperature of the refrigerant can be lowered.

The refrigerant may be selected depending on a type of the refrigeratingsystem because the refrigerating temperature to be realized at theevaporator 4 depends on a refrigerant to be used. For example, the aboveblended refrigerant of R-125 and R-21 is suitable for a refrigerator ofdomestic use requiring refrigerating temperatures of approximately -20°to -40° C., and the blended refrigerant of R-23 and R-21 is suitable fora refrigerator of very low temperatures requiring refrigeratingtemperatures of approximately -80° C.

In this case, as the boiling point of R-21 is relatively high, too largemixing ratio of R-21 hinders realization of the required refrigeratingtemperatures at the evaporator 4; in contrast, too small mixing ratiothereof degrades the oil-returning function. From the above view point,the mixing ratio of R-21 should be selected from the range of 0.1-50 wt%. Especially in the combination of R-21 and R-125, the content of R-21is suitably 5-15 wt %, preferably 7-12 wt %. In the combination of R-21and R-23, the content of R-21 is suitably 30-50 wt %, preferably 35-45wt %.

Other refrigerant compositions applicable to the refrigerant circuitshown in FIG. 1 are a combination of R-22 and R-21, and that of R-142band R-21. In these combinations, the content of R-21 is suitably 5-25 wt%, preferably 10-15 %. In the combination of R-21 and R-142b, althoughR-142b is flammable, mixing R-21 thereto enables to maintain the blendwithin a nonflammable area. FIG. 3 shows such a nonflammable area.

Here, described is another example of the invention in which arefrigerant composition of a combination of R-22, R-142b, and R-21 isused in a refrigerant circuit shown in FIG. 2. This refrigerant circuitis a refrigerating cycle for the blended refrigerant of R-22, R-142b,and R-21. In FIG. 2, the same reference numerals as in FIG. 1 designatethe same parts. An outlet piping 5 of a compressor 1 connects to acondenser 2 which links to a gas-liquid separator 6. A liquid conductingpiping 7 extending from the gas-liquid separator 6 connects to acapillary tube 8 which links to an intermediate heat exchanger 9. On theother hand, a gas conducting piping 10 extending from the gas-liquidseparator 6 passes through the intermediate heat exchanger 9 andconnects to a capillary tube 11 which links to an evaporator 4. A piping12 extending from the intermediate heat exchanger 9 and a piping 13extending from the evaporator 4 joins together at a junction P andconnect to an inlet piping 14 of the compressor 1.

The refrigerant circuit in FIG. 2 is charged with a non-azeotropicmixture of R-22, R-142b, and R-21. Description of an operation of thecircuit follows. A high temperature and high pressure gas of the aboveblended refrigerant discharged from the compressor 1 flows into thecondenser 2 to dissipate its heat, whereby most part of R-142b and R-21is liquefied and flows into the gas-liquid separator 6. The liquid ofR-142b and R-21, and R-22 still in a gaseous form are separated there,the former is conducted to the liquid conducting piping 7 while thelatter being conducted to the gas conducting piping 10. R-142b and R-21passing through the liquid conducting piping 7 flow into the capillarytube 8 in which their pressure is reduced, and then flow into theintermediate heat exchanger 9 in which R-142b evaporates. On the otherhand, R-22 passing through the gas conducting piping 10 is cooled andcondensed when passing through the intermediate heat exchanger 9 byR-142 which evaporates there. R-22 is then reduced in its pressure inthe capillary tube 11 and flows into the evaporator 4 where itevaporates for refrigerating. R-142b and R-21 flowing out of theintermediate heat exchanger 9 and R-22 flowing out of the evaporator 4pass through the pipings 12 and 13 respectively, join together at thejunction P to form again the mixture of R-22, R-142b, and R-21, andreturn to the compressor 1.

The compressor oil which is entrained in the refrigerant circuit, isdissolved in R-21 and returned to the compressor. R-21 having beenreturned to the compressor 1 evaporates there so that the compressor 1is cooled. Therefore, an compressor outlet temperature of therefrigerant can be further lowered.

When contents of the refrigerant used in the refrigerant circuit is tobe decided, it should be considered that too much R-21 renders R-142more non-explosive and more safe, however, the refrigerating capabilityat the evaporator 4 degrades so that the refrigerant cannot be used fora refrigerator. Further to be considered are compatibility of therefrigerant with compressor oils and an compressor outlet temperature ofthe refrigerant. In view of the above considerations, it is preferableto mix 2-12 wt % of R-21, 50-93 wt % of R-22, and 5-48 wt % of R-142b.For example, the refrigerant having 57 wt % of R-22, 38 wt % of R-142b,and 5 wt % of R-21 has attained a refrigerating temperature of -40° C.and exhibited a high explosion-proof characteristic. Further, therefrigerant having 70 wt % of R-22, 25 wt % of R-142b, and 5 % of R-21has been able to attain a lower refrigerating temperature than above.

Since the refrigerating temperature of -40° C. can be obtained, thisrefrigerant composition can be advantageously used in variousrefrigerating systems for either industrial or domestic use.

For better understanding, FIG. 5 shows variations of a compressortemperature and a refrigerating temperature at the evaporator withrespect to the refrigerant composition whose content ratios are varied,however, a ratio of R-22 to R-142b is constant (74:26).

According to the present invention, refrigerant compositions havingconsiderably reduced depletion potentials of ozone in the ozonospherecan be obtained. Further, dichloromonofluoromethane (R-21) of therefrigerant compositions is compatible with compressor oils so that theoil entrained in the refrigerant circuit can be returned to thecompressor thereby preventing seizing of the compressor. Furthermore,R-21 of the refrigerant compositions functions to cool the compressorthereby aiding in preventing oil-sludge.

Further according to the invention, in the case that refrigerantcompositions are prepared by blending 1-chloro-1,1-difluoroethane(R-142b), R-21 of the refrigerant compositions can maintain thecompositions within a nonflammable area, so that eventual explosion of1-chloro-1,1-difluoroethane can be prevented even if leakage of therefrigerant from the refrigerant circuit may occurs.

Still further according to the invention, by determining the ratio ofR-21 to R-142b within the range of 5-20 wt %, degradation of therefrigerating capability caused by blending R-21 having a high boilingpoint can be prevented thereby assuring the refrigerating capability andexplosion-proof characteristic of the refrigerant compositions.

It should be noticed that a non-azeotropic refrigerant composition ofR-22, R-142b, and R-134a is also applicable to the refrigerant circuitshown in FIG. 2. R-134a of this refrigerant composition circulates inthe refrigerant circuit as described above with respect to R-21. In thiscase, the compressor oil is dissolved in R-134a and returned to thecompressor 1. However, since R-134a is not compatible with naphthenicoils, it is required to use alkylbenzoic oils as the compressor oil.Further, since the amount of R-134a which can be dissolved even in analkylbenzoic oil is limited, the content of R-134a should be determinedwithin the limited soluble range.

According to the experiments, it was found that a suitable mixing ratioof R-134a to the total weight of the refrigerant composition was 5 %.Accordingly, the mixing ratios of the refrigerant composition wasdetermined as 70 wt % of R-22, 25 wt % of R-142b, and 5 % of R-134a.According to the experiments using the refrigerant composition of theabove contents, a refrigerating temperature of -30° C. was attained atthe evaporator 4 under the atmospheric temperature, and at the same timeR-134a was dissolved in the compressor oil thereby enjoying asatisfactory oil-returning effect.

What is claimed is:
 1. A refrigerant composition consisting essentiallyof from 50 to 0.1 wt % of dichloromonofluoromethane and respectivelyfrom 50 to 99.9 wt % of at least one fluoroalkyl compound selected fromthe group consisting of trifluoromethane, pentafluoroethane,monochlorodifluoromethane and 1-chloro-1,1-difluoroethane.
 2. Therefrigerant composition as set forth in claim 1, which comprisesdichloromonofluoromethane and a fluoroalkyl compound selected from thegroup consisting of trifluoromethane, pentafluoroethane and mixturesthereof.
 3. The refrigerant composition as set forth in claim 1, whichcomprises dichloromonofluoromethane and a fluoroalkyl compound selectedfrom the group consisting of monochlorodifluoromethane,1-chloro-1,1-difluoroethane and mixtures thereof.
 4. The refrigerantcomposition as set forth in claim 1, which is prepared so that arefrigerating temperature thereof at an evaporator can be -20° C. andbelow.
 5. The refrigerant composition as set forth in claim 1, which isprepared so that a refrigerating temperature thereof at an evaporatorcan be -40° C. and below.
 6. The refrigerant composition as set forth inclaim 1, which contains 30-50 wt % of dichloromonofluoromethane.
 7. Therefrigerant composition as set forth in claim 3, which comprises 2-12 wt% of dichloromonofluoromethane, 50-93 wt % of chlorodifluoromethane and5-48 wt % of 1-chloro-1,1-difluoroethane.